The objective of this program project is the study of the pathophysiology of thrombosis. The work of the group is focused on the interaction of proteolytic enzymes, fibrinogen and platelets. A major aim is to obtain quantitative information on the roles of the different activation and inhibition mechanisms in thrombosis and intra-vascular coagulation. This aim is being approached by developing specific and quantitative tests for the action of thrombin, plasmin, factor XIIIa and for platelet activation in vivo. The tests are to be applied to in vitro studies designed to gain new information concerning the thrombotic process as well as to studies in animal models and to patients with thrombotic disease. It is hoped that this information will facilitate the development of improved diagnostic, therapeutic and preventive methods for thrombotic disease.